Flutter uses one Dart codebase to ship Android and iOS apps, which usually means faster delivery and lower cost for startups and business apps.
Swift and SwiftUI give the deepest access to Apple features and the most native feel, so they suit iOS-first products and apps that rely on advanced device capabilities.
If you need both platforms on a modest budget, Flutter is often the practical choice. If iPhone users are your main audience, Swift is worth it.
The right answer depends on your features, timeline and budget. Share your idea and we will recommend an approach.